The invention relates to an ozone water purifying apparatus with the following features: a tank is provided, which exhibits at the top a manhole closable by means of a cover. A treatment unit, which consists of an ozoniser and a mixer, is fastened to the interior of the cover. The treatment unit has an inlet pipe pointing vertically downwards, and lateral outlet orifices. The tank has a feed orifice and a return orifice, and preferably a filter bed.
It is necessary for the interior of the tank of such an apparatus to be accessible from above, particularly if it is simultaneously a filter tank. The filter bed is generally composed of a plurality of layers of different sands or gravels. They rest upon a perforated bottom, also called a nozzle bottom, or else a so-called filter spider is located in a lower coarse-grain layer and collects the filtered water in the lower region, so that it can be withdrawn from the tank via the return orifice. It is necessary for the apparatuses mentioned to be installed in the tank and to be accessible from time to time for inspection or cleaning, in order to exchange the sand charge, for example.
For this reason, in an apparatus of the type initially designed, and disclosed, for example, in German Pat. No. 2,412,770, the treatment unit together with its complete water feed means is fitted on the cover of the tank and can therefore be removed by lifting off the cover. The peculiarity of this known apparatus lies, inter alia, in the very fact that the treatment unit is not fitted outside the tank, but is immersed in the water charge of the tank, which extends virtually to the top. The reason for this is that the ozoniser which forms a part of the treatment unit needs to be cooled, and in this manner dissipates its heat advantageously to the water to be purified. The ozone transport path is also extremely short. More specifically, in the known apparatus the problem of the water feed is solved in that the feed pipe penetrates the cover and is connected permanently to the inlet pipe of the treatment unit by means of a 180.degree. bend. The feed pipe together with the 180.degree. bend is therefore also removed when the cover and the treatment unit are lifted out.
However, the known design ceases to be satisfactory for larger, and larger-capacity, water treatment apparatuses. The considerable hydraulic resistance of the 180.degree. bend becomes a disturbing factor. The feed pipe passage arranged eccentrically on the cover necessitates a larger cover diameter than is necessary for the passage of a fitter, and desirable from the standpoint of standardising the components of such an apparatus. The sealing difficulties increase disproportionally with the diameter of the cover.
The water feed pipe, which is brought in from above and penetrates the cover, also obstructs the arrangement and maintenance of electrical auxiliary units of the treatment unit which are located on the top side of the cover.